Selective activation of prodrugs in breast cancer using metabolic glycoengineering and the tetrazine ligation bioorthogonal reaction.

Increasing the selectivity of chemotherapies by converting them into prodrugs that can be activated at the tumour site decreases their side effects and allows discrimination between cancerous and non-cancerous cells. Herein, the use of metabolic glycoengineering (MGE) to selectively label MCF-7 breast cancer cells with tetrazine (Tz) activators for subsequent activation of prodrugs containing the trans-cyclooctene (TCO) moiety by a bioorthogonal reaction is demonstrated. Three novel Tz-modified monosaccharides, Ac4ManNTz 7, Ac4GalNTz 8, and Ac4SiaTz 16, were used for expression of the Tz activator within sialic-acid rich breast cancer cells' surface glycans through MGE. Tz expression on breast cancer cells (MCF-7) was evaluated versus the non-cancerous L929 fibroblasts showing a concentration-dependant effect and excellent selectivity with ≥35-fold Tz expression on the MCF-7 cells versus the non-cancerous L929 fibroblasts. Next, a novel TCO-N-mustard prodrug and a TCO-doxorubicin prodrug were analyzed in vitro on the Tz-bioengineered cells to probe our hypothesis that these could be activated via a bioorthogonal reaction. Selective prodrug activation and restoration of cytotoxicity were demonstrated for the MCF-7 breast cancer cells versus the non-cancerous L929 cells. Restoration of the parent drug's cytotoxicity was shown to be dependent on the level of Tz expression where the Ac4ManNTz 7 and Ac4GalNTz 8 derivatives (20 µM) lead to the highest Tz expression and full restoration of the parent drug's cytotoxicity. This work suggests the feasibility of combining MGE and tetrazine ligation for selective prodrug activation in breast cancer.

Elevated concentrations of Neu5Ac and Neu5,9Ac2 in human plasma: potential biomarkers of cardiovascular disease.

Cardiovascular disease (CVD) is a group of health conditions affecting the heart and vascular system with very high prevalence and mortality rates. The presence of CVD is characterised by high levels of inflammation which have previously been associated with increased plasma concentrations of N-acetyl neuraminic acid (Neu5Ac). While Neu5Ac has been studied in the context of CVD, Neu5,9Ac2 has not, despite being the second most abundant sialic acid in human plasma. A small-scale pilot study of thirty plasma samples from patients with diagnosed CVD, and thirty age and sex-matched healthy controls, was designed to gain insight into sialic acids as biomarkers for CVD and potential future areas of study. Each sample was assayed for Neu5Ac and Neu5,9Ac2 concentrations. Mean Neu5Ac and Neu5,9Ac2 concentrations were significantly elevated in patients with CVD compared to healthy controls (Neu5Ac: P < 0.001; Neu5,9Ac2: P < 0.04). Receiver operator curve (ROC) analysis indicated that both Neu5Ac and Neu5,9Ac2 have reasonable predictive power for the presence of CVD (Neu5Ac AUC: 0.86; Neu5,9Ac2 AUC: 0.71). However, while Neu5Ac had both good sensitivity (0.82) and specificity (0.81), Neu5,9Ac2 had equivalent specificity (0.81) but very poor sensitivity (0.44). A combination marker of Neu5Ac + Neu5,9Ac2 showed improvement over Neu5Ac alone in terms of predictive power (AUC: 0.93), sensitivity (0.87), and specificity (0.90). Comparison to a known inflammatory marker, high sensitivity c-reactive protein (hs-CRP: P-value: NS, ROC:0.50) was carried out, showing that both Neu5Ac and Neu5,9Ac2 outperformed this marker. Further to this, hs-CRP values were combined with the three different sialic acid markers to determine any effect on the AUC values. A slight improvement in AUC was noted for each of the combinations, with Neu5Ac + Neu5,9Ac2 + hs-CRP giving the best AUC of 0.97 overall. Thus, Neu5Ac would appear to offer good potential as a predictive marker for the presence of CVD, which the addition of Neu5,9Ac2 predictive power improves, with further improvement seen by the addition of hs-CRP.

Bioorthogonal activation of prodrugs, for the potential treatment of breast cancer, using the Staudinger reaction.

Selective prodrug activation at a tumor site is crucial to maximise the efficiency of chemotherapy approaches and minimise side effects due to off-site activation. In this paper, a new prodrug activation strategy is reported based on the bioorthogonal Staudinger reaction. The feasibility of this prodrug activation strategy was initially demonstrated using 9-azido sialic acid 4 as a trigger and two novel triphenylphosphine-modified N-mustard-PRO 10 and doxorubicin-PRO 12 prodrugs in an HPLC-monitored release study. Then, the azide reporter group was introduced on cancer cells' surfaces through metabolic glycoengineering of sialic acid-rich surface glycans using azide-modified monosaccharides (9-azido sialic acid 4, tetra-O-acetylated-9-azido sialic acid 5 and tetra-O-acetyl azidomannosamine). Next, the N-mustard-PRO 10 and doxorubicin-PRO 12 prodrugs were employed in vitro with the bioengineered cells, and activation of the prodrugs, which allowed selective release of the cytotoxic moiety at the tumour cell, was assessed. Release of the parent drugs from the prodrugs was shown to be dependent on the level of metabolic labelling, where tetra-O-acetyl azidomannosamine allowed the highest level of azide reporter generation in tumor cells and led to full recovery of the parent cytotoxic drug's potency. The selectivity of azide expression on breast cancer MCF-7 cells versus normal fibroblast L929 cells was also probed, with the 9-azido sialic acid and tetra-O-acetylated-9-azido sialic acid showing ∼17-fold higher azide expression on the former. Taken together, these data demonstrate the feasibility of the Staudinger reaction for selective activation of prodrugs targeted to the MCF-7 breast cancer cells.

Anticancer evaluation of new organometallic ruthenium(ii) flavone complexes.

Targeting multiple malignancy features such as angiogenesis, proliferation and metastasis with one molecule is an effective strategy in developing potent anticancer agents. Ruthenium metal complexation to bioactive scaffolds is reported to enhance their biological activities. Herein, we evaluate the impact of Ru chelation on the pharmacological activities of two bioactive flavones (1 and 2) as anticancer candidates. The novel Ru complexes (1Ru and 2Ru) caused a loss of their parent molecules' antiangiogenic activities in an endothelial cell tube formation assay. 1Ru enhanced the antiproliferative and antimigratory activities of its 4-oxoflavone 1 on MCF-7 breast cancer cells (IC50 = 66.15 ± 5 µM and 50% migration inhibition, p < 0.01 at 1 µM). 2Ru diminished 4-thioflavone's (2) cytotoxic activity on MCF-7 and MDA-MB-231 yet significantly enhanced 2's migration inhibition (p < 0.05) particularly on the MDA-MB-231 cell line. The test derivatives also showed non-intercalative interaction with VEGF and c-myc i-motif DNA sequences.

In Vivo Applications of Bioorthogonal Reactions: Chemistry and Targeting Mechanisms.

Bioorthogonal chemistry involves selective biocompatible reactions between functional groups that are not normally present in biology. It has been used to probe biomolecules in living systems, and has advanced biomedical strategies such as diagnostics and therapeutics. In this review, the challenges and opportunities encountered when translating in vitro bioorthogonal approaches to in vivo settings are presented, with a focus on methods to deliver the bioorthogonal reaction components. These methods include metabolic bioengineering, active targeting, passive targeting, and simultaneously used strategies. The suitability of bioorthogonal ligation reactions and bond cleavage reactions for in vivo applications is critically appraised, and practical considerations such as the optimum scheduling regimen in pretargeting approaches are discussed. Finally, we present our own perspectives for this area and identify what, in our view, are the key challenges that must be overcome to maximise the impact of these approaches.

Biomolecular Corona Stability in Association with Plasma Cholesterol Level.

Biomolecular corona is spontaneously formed on the surface of nanoparticles (NPs) when they are in contact with biological fluids. It plays an important role in the colloidal stability of NPs, which is of importance for most of their medical applications and toxicity assessment. While typical studies use either blood plasma or serum from a pooled biobank, it is unclear whether differences in the media, such as cholesterol level or protein concentration, might affect the NP colloidal stability and corona composition. In this study, the silica corona was prepared at particularly low plasma concentrations (3%, v/v-1.98 mg/mL) to identify the critical roles of the protein mass/NP surface ratio and the level of plasma cholesterol on the corona protein pattern and particle stability. While depending on the plasma dilution factor, the corona protein composition could be controlled by keeping the protein/NP constant. The NP colloidal stability was found to strongly correlate with the level of cholesterol in human plasma, particularly due to the high enrichment of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) in the corona. A cohort study on plasma samples from individuals with known cholesterol levels was performed to highlight that association, which could be relevant for all corona systems enriched with the LDL.

Halogenated Flavonoid Derivatives Display Antiangiogenic Activity.

Antiangiogenic agents attenuate tumours' growth and metastases and are therefore beneficial as an adjuvant or standalone cancer regimen. Drugs with dual antiproliferative and antiangiogenic activities can achieve anticancer efficacy and overcome acquired resistance. In this study, synthetic flavones (5a,b) with reported anticancer activity, and derivatives (4b and 6a), exhibited significant inhibition of endothelial cell tube formation (40-55%, 12 h) at 1 µM, which is comparable to sunitinib (50% inhibition at 1 µM, 48 h). Flavones (4b, 5a,b and 6a) also showed 25-37% reduction in HUVECs migration at 10 µM. In a Western blotting assay, 5a and 5b subdued VEGFR2 phosphorylation by 37% and 57%, respectively, suggesting that VEGFR2 may be their main antiangiogenic target. 5b displayed the best docking fit with VEGFR2 in an in silico study, followed by 5a, emphasizing the importance of the 7-hydroxyl group accompanied by a 4-C=S for activity. Conversely, derivatives with a 4-carbonyl moiety fitted poorly into the target's binding pocket, suggesting that their antiangiogenic activity depends on a different target. This study provides valuable insight into the Structure Activity Relationships (SAR) and modes of action of halogenated flavones with VEGFR2 and highlights their therapeutic potential as antiangiogenic/anticancer lead compounds.

Label-free 1D microfluidic dipstick counting of microbial colonies and bacteriophage plaques.

Counting viable bacterial cells and functional bacteriophage is fundamental to microbiology underpinning research, surveillance, biopharmaceuticals and diagnostics. Colony forming unit (CFU) and plaque forming unit (PFU) counting still requires slow and laborious solid culture on agar in Petri dishes or plates. Here, we show that dip-stick microfluidic strips can be used without growth indicator dye for rapid and simple CFU ml-1 and PFU ml-1 measurement. We demonstrate for the first time that fluoropolymer microcapillaries combined with digital imaging allow bacteriophage plaques to be counted rapidly in a dip-and-test format. The microfluidic length scales offer a linear 1-dimensional alternative to a 2D solid agar medium surface, with colonies or plaques clearly visible as "dashes" or "gaps". An inexpensive open source darkfield biosensor system using Raspberry Pi imaging permits label-free detection and counting of colonies or plaques within 4-8 hours in a linear, liquid matrix within ∼200 µm inner diameter microcapillaries. We obtained full quantitative agreement between 1D microfluidic colony counting in dipsticks versus conventional 2D solid agar Petri dish plates for S. aureus and E. coli, and for T2 phage and phage K, but up to 6 times faster. Time-lapse darkfield imaging permitted detailed kinetic analysis of colony growth in the microcapillaries, providing new insight into microfluidic microbiology and colony growth, not possible with Petri dishes. Surprisingly, whilst E. coli colonies appeared earlier, subsequent colony expansion was faster along the microcapillaries for S. aureus. This may be explained by the microenvironment offered for 1D colony growth within microcapillaries, linked to a mass balance between nutrient (glucose) diffusion and bacterial growth kinetics. Counting individual colonies in liquid medium was not possible for motile strains that spread rapidly along the capillary, however inclusion of soft agar inhibited spreading, making this new simple dip-and-test counting method applicable to both motile and non-motile bacteria. Label-free dipstick colony and plaque counting has potential for many analytical microbial tasks, and the innovation of 1D colony counting has relevance to other microfluidic microbiology.

Glycosides of Nadifloxacin-Synthesis and Antibacterial Activities against Methicillin-Resistant Staphylococcus aureus.

The increase in the number of bacteria that are resistant to multiple antibiotics poses a serious clinical problem that threatens the health of humans worldwide. Nadifloxacin (1) is a highly potent antibacterial agent with broad-spectrum activity. However, its poor aqueous solubility has limited its use to topical applications. To increase its solubility, it was glycosylated herein to form a range of trans-linked (3a-e) and cis-linked (7a,b) glycosides, each of which was prepared and purified to afford single anomers. The seven glycoside derivatives (3a-e, 7a,b) were examined for potency against eight strains of S. aureus, four of which were methicillin-resistant. Although less potent than free nadifloxacin (1), the α-L-arabinofuransoside (3a) was effective against all strains that were tested (minimum inhibitory concentrations of 1-8 µg/mL compared to 0.1-0.25 µg/mL for nadifloxacin), demonstrating the potential of this glycoside as an antibacterial agent. Estimation of Log P as well as observations made during preparation of these compounds reveal that the solubilities of the glycosides were greatly improved compared with nadifloxacin (1), raising the prospect of its use in oral applications.

Impacts of Commonly Used Edible Plants on the Modulation of Platelet Function.

Cardiovascular diseases (CVDs) are a primary cause of deaths worldwide. Thrombotic diseases, specifically stroke and coronary heart diseases, account for around 85% of CVDs-induced deaths. Platelets (small circulating blood cells) are responsible for the prevention of excessive bleeding upon vascular injury, through blood clotting (haemostasis). However, unnecessary activation of platelets under pathological conditions, such as upon the rupture of atherosclerotic plaques, results in thrombus formation (thrombosis), which can cause life threatening conditions such as stroke or heart attack. Therefore, antiplatelet medications are usually prescribed for people who are at a high risk of thrombotic diseases. The currently used antiplatelet drugs are associated with major side effects such as excessive bleeding, and some patients are resistant to these drugs. Therefore, numerous studies have been conducted to develop new antiplatelet agents and notably, to establish the relationship between edible plants, specifically fruits, vegetables and spices, and cardiovascular health. Indeed, healthy and balanced diets have proven to be effective for the prevention of CVDs in diverse settings. A high intake of fruits and vegetables in regular diet is associated with lower risks for stroke and coronary heart diseases because of their plethora of phytochemical constituents. In this review, we discuss the impacts of commonly used selected edible plants (specifically vegetables, fruits and spices) and/or their isolated compounds on the modulation of platelet function, haemostasis and thrombosis.

Conjugation to PEG as a Strategy to Limit the Uptake of Drugs by the Placenta: Potential Applications for Drug Administration in Pregnancy.

Here, we evaluated the feasibility of non-prodrug PEG-drug conjugates to decrease the accumulation of drugs within the placental tissues. The results showed that PEG was biocompatible with the human placenta with no alteration of the basal rate of proliferation or apoptosis in term placental explants. No significant changes in the released levels of lactate dehydrogenase and the human chorionic gonadotropin were observed after PEG treatment. The cellular uptake studies revealed that conjugating Cy5.5 and haloperidol to PEG significantly reduced (by up to ∼40-fold) their uptake by the placenta. These findings highlight the viability of novel non-prodrug polymer-drug conjugates to avoid the accumulation of drugs within the placenta.

Quantitative Standards of 4-O-Acetyl- and 9-O-Acetyl-N-Acetylneuraminic Acid for the Analysis of Plasma and Serum.

N-Acetylneuraminic acid (sialic acid, Neu5Ac) is one of a large, diverse family of nine-carbon monosaccharides that play roles in many biological functions such as immune response. Neu5Ac has previously been identified as a potential biomarker for the presence and pathogenesis of cardiovascular disease (CVD), diabetes and cancer. More recent research has highlighted acetylated sialic acid derivatives, specifically Neu5,9Ac2 , as biomarkers for oral and breast cancers, but advances in analysis have been hampered due to a lack of commercially available quantitative standards. We report here the synthesis of 9-O- and 4-O-acetylated sialic acids (Neu5,9Ac2 and Neu4,5Ac2 ) with optimisation of previously reported synthetic routes. Neu5,9Ac2 was synthesised in 1 step in 68 % yield. Neu4,5Ac2 was synthesised in 4 steps in 39 % overall yield. Synthesis was followed by analysis of these standards via quantitative NMR (qNMR) spectroscopy. Their utilisation for the identification and quantification of specific acetylated sialic acid derivatives in biological samples is also demonstrated.

Counting bacteria in microfluidic devices: Smartphone compatible 'dip-and-test' viable cell quantitation using resazurin amplified detection in microliter capillary arrays.

Viable bacterial cell counting is fundamental to analytical microbiology and agar plate colony counting remains common yet laborious and slow. Here, we demonstrate two methods for counting bacteria using commercially available microfluidic devices. We show that accurate viable cell counting is possible using simple and easy 'dip and test' arrays of microcapillaries. Colorimetric and fluorescent growth detection both permit viable cell counting in microcapillaries either by limiting dilution into multiple microfluidic compartments using a single endpoint measurement, or alternatively by quantifying growth kinetics. The microcapillary devices are compatible with conventional 96 well plates and multichannel pipettes, expanding each microplate row into 120 individual 1 or 2 µL samples. At limiting dilution, counting the proportion of positive compartments permitted accurate calculation of gram-negative and gram-positive bacteria (E. coli and S. saprophyticus) at concentrations down to as low as 10 CFU/mL with almost 1:1 agreement with agar plate colony counts over four orders of magnitude. A smartphone camera was sufficient to record endpoint images of resazurin growth detection both colorimetrically and fluorescently. Viable cell counting of E. coli and S. saprophyticus was also possible through recording growth kinetics and determining the time taken to detect resazurin conversion. However, only the limiting dilution method remained consistent in the presence of urine matrix, as some interference in growth rate was observed when bacteria were spiked into higher concentrations of normal urine to simulate urinary tract infection patient samples. However, with the limiting dilution counting method endpoint growth was always detected even in the presence of 90% urine matrix, suggesting that this method might permit bacterial pathogen counting directly in clinical samples without agar plating.

Assays for the identification and quantification of sialic acids: Challenges, opportunities and future perspectives.

N-Acetyl neuraminic acid (sialic acid) is a monosaccharide generally found as the terminating unit on glycans, which in turn are found on the surface of cells and glycoproteins. These glycans aid in a variety of biological functions such as cell interactions and immune response. Sialic acid has been identified as a biomarker for cardiovascular disease, diabetes and a range of other inflammatory and degenerative conditions. It has also been identified as a marker for different types of cancer. Sialic acid levels vary depending on the level of inflammation present during the course of an inflammatory disease and it is overexpressed by tumours as a shield against the immune system. Since the discovery of sialic acid, numerous assays have been developed for the identification and quantification of different sialic acid derivative monosaccharides and these assays fall into four main groups: colorimetric, fluorometric, enzymatic and chromatographic/mass spectrometric, with much overlap between these. Given the importance of sialic acids in biological pathways, this review article critically appraises assays that are used to detect and quantify sialic acid and its derivatives. Thus it details the method, sensitivity, specificity and wider scope of a range of assays, and concludes by suggesting some future directions for assay development and application. In this way, insight is provided into assays that allow for the accurate quantitation of sialic acid in biological samples, which may facilitate identification of the roles of sialic acid in healthy and disease pathways.

New pyridine and chromene scaffolds as potent vasorelaxant and anticancer agents.

Based on studies that have reported the association between cancer and cardiovascular diseases, new series of pyridine- (3a-o) and/or chromene- (4a-e) carbonitrile analogous were designed, synthesized and screened for their vasodilation and cytotoxic properties. The majority of the new chemical entities demonstrated significant vasodilation efficacies, compounds 3a, 3h, 3j, 3m, 3o, 4d and 4e exhibited the most promising potency with IC50 = 437.9, 481.0, 484.5, 444.8, 312.1, 427.6 and 417.2 µM, respectively, exceeding prazosin hydrochloride (IC50 = 487.3 µM). Compounds 3b-e, 3k and 3l also, revealed moderate vasodilation activity with IC50 values ranging from 489.7 to 584.5 µM. In addition, the anti-proliferative activity evaluation of the experimental compounds at 10 µM on the MCF-7 and MDA-MB 231 breast cancer cell lines illustrated the excellent anti-proliferative properties of derivatives 3d, 3g and 3i. Compound 3d was the most potent analogue with IC50 = 4.55 ± 0.88 and 9.87 ± 0.89 µM against MCF-7 and MDA-MB 231, respectively. Moreover, compound 3d stimulated apoptosis and cell cycle arrest at the S phase in MCF-7 cells in addition to its capability in accumulation of cells in pre-G1 phase and activating caspase-3. Furthermore, the molecular docking of 3d was performed to discover the binding modes within the active site of caspase-3. 3d, as the only common bi-functional agent among the tested hits, demonstrated that new pyridine-3-carbonitrile derivatives bearing cycloheptyl ring systems offer potential as new therapeutic candidates with combined vasodilation and anticancer properties.

Antiangiogenic Activity of Flavonoids: A Systematic Review and Meta-Analysis.

Abstract: An imbalance of angiogenesis contributes to many pathologies such as cancer, arthritis and retinopathy, hence molecules that can modulate angiogenesis are of considerable therapeutic importance. Despite many reports on the promising antiangiogenic properties of naturally occurring flavonoids, no flavonoids have progressed to the clinic for this application. This systematic review and meta-analysis therefore evaluates the antiangiogenic activities of a wide range of flavonoids and is presented in two sections. The first part of the study (Systematic overview) included 402 articles identified by searching articles published before May 2020 using ScienceDirect, PubMed and Web of Science databases. From this initial search, different classes of flavonoids with antiangiogenic activities, related pathologies and use of in vitro and/or in/ex vivo angiogenesis assays were identified. In the second part (Meta-analysis), 25 studies concerning the antiangiogenic evaluation of flavonoids using the in vivo chick chorioallantoic membrane (CAM) assay were included, following a targeted search on articles published prior to June 2020. Meta-analysis of 15 out of the 25 eligible studies showed concentration dependent antiangiogenic activity of six compared subclasses of flavonoids with isoflavones, flavonols and flavones being the most active (64 to 80% reduction of blood vessels at 100 µM). Furthermore, the key structural features required for the antiangiogenic activity of flavonoids were derived from the pooled data in a structure activity relationship (SAR) study. All in all, flavonoids are promising candidates for the development of antiangiogenic agents, however further investigations are needed to determine the key structural features responsible for their activity.

Conjugation of haloperidol to PEG allows peripheral localisation of haloperidol and eliminates CNS extrapyramidal effects.

We have previously reported the synthesis of a poly(ethylene glycol)-haloperidol (PEG-haloperidol) conjugate that retained affinity for its target D2 receptor and was stable in simulated physiological conditions. We hypothesised that this polymer-drug conjugate would localise haloperidol's activity either centrally or peripherally, dependent on the location of administration, due to the polymer preventing penetration through the blood-brain barrier (BBB). Herein, we validate this hypothesis using in vitro and in vivo studies. We first demonstrate, via a [35S]GTPγS-binding assay, that drug activity is retained after conjugation to the polymer, supportive of retention of effective therapeutic ability. Specifically, the PEG-haloperidol conjugate (at 10 and 100 nM) was able to significantly inhibit dopamine-induced G-protein activation via D2 receptors, albeit with a loss of potency compared to the free haloperidol (~18-fold at 10 nM). This loss of potency was further probed and rationalised using molecular docking experiments, which indicated that conjugated haloperidol can still bind to the D2 receptors, albeit with a flipped orientation in the binding pocket within the receptor, which may explain the reduced activity. Finally, rat catalepsy studies confirmed the restricted permeation of the conjugate through the BBB in vivo. Rats treated intravenously with free haloperidol became cataleptic, whereas normal behaviour was observed in rats that received the PEG-haloperidol conjugate, suggesting that conjugation can effectively prevent unwanted central effects. Taken together these results demonstrate that conjugating small molecules to polymers is effective at prohibiting penetration of the drug through the BBB and is a valid targeting strategy for drugs to facilitate peripheral (or central) effects without inducing side effects in other compartments.

Synthetic Flavonoids as Novel Modulators of Platelet Function and Thrombosis.

Cardiovascular diseases represent a major cause of mortality and morbidity in the world, and specifically, thrombotic conditions such as heart attacks and strokes are caused by unwarranted activation of platelets and subsequent formation of blood clots (thrombi) within the blood vessels during pathological circumstances. Therefore, platelets act as a primary therapeutic target to treat and prevent thrombotic conditions. Current treatments are limited due to intolerance, and they are associated with severe side effects such as bleeding complications. Hence, the development of novel therapeutic strategies for thrombotic diseases is an urgent priority. Flavonoids are naturally occurring plant-derived molecules that exert numerous beneficial effects in humans through modulating the functions of distinct cell types. However, naturally occurring flavonoids suffer from several issues such as poor solubility, lipophilicity, and bioavailability, which hinder their efficacy and potency. Despite these, flavonoids act as versatile templates for the design and synthesis of novel molecules for various therapeutic targets. Indeed, several synthetic flavonoids have recently been developed to improve their stability, bioavailability, and efficacy, including for the modulation of platelet function. Here, we provide insight into the actions of certain natural flavonoids along with the advantages of synthetic flavonoids in the modulation of platelet function, haemostasis, and thrombosis.

Synthesis and antibacterial profiles of targeted triclosan derivatives.

There is an ongoing urgent need for new targeted antibacterial compounds with novel mechanisms of action for the treatment of infections caused by bacteria that are resistant to currently available materials. Since the expression of glycosidase enzymes within bacteria is unequally distributed, glycoside derivatives of antibacterial agents offer potential as targeted prodrugs for bacterial infections. Herein we report the synthesis and characterisation of four α-D-glycopyranosides and three ß-D-glycopyranosides of the broad antibacterial agent triclosan, in generally good synthetic yields, and with excellent purities. Each glycoside was analysed to determine its ability to inhibit the growth of a wide range of Gram-negative and Gram-positive organisms, including many of clinical significance. All of the triclosan glycosides that were synthesized demonstrated antibacterial activity against many of the organisms that were examined. For example, ß-galactoside (3a) and α-arabinoside (3c) had MIC values of 0.5 µg/ml for several strains of S. aureus and S. haemolyticus. The triclosan glycosides were also generally found to be more water soluble and much more selective than the underivatized triclosan, making them ideal both for the targeted inhibition of bacterial growth and as agents for the selective recovery of bacteria from mixed cultures. In the latter case, two Bacillus strains could be identified from various strains of Bacillus and Staphylococcus after inoculation onto Nutrient Agar No. 2 with 0.25 µg/ml triclosan-α-D-glucopyranoside (3e). This glucoside may, therefore, be of use for the isolation and identification of the food-poisoning organism Bacillus cereus.

Impact of specific functional groups in flavonoids on the modulation of platelet activation.

Flavonoids exert innumerable beneficial effects on cardiovascular health including the reduction of platelet activation, and thereby, thrombosis. Hence, flavonoids are deemed to be a molecular template for the design of novel therapeutic agents for various diseases including thrombotic conditions. However, the structure-activity relationships of flavonoids with platelets is not fully understood. Therefore, this study aims to advance the current knowledge on structure-activity relationships of flavonoids through a systematic analysis of structurally-related flavones. Here, we investigated a panel of 16 synthetic flavones containing hydroxy or methoxy groups at C-7,8 positions on the A-ring, with a phenyl group or its bioisosteres as the B-ring, along with their thio analogues possessing a sulfur molecule at the 4th carbon position of the C-ring. The antiplatelet efficacies of these compounds were analysed using human isolated platelets upon activation with cross-linked collagen-related peptide by optical aggregometry. The results demonstrate that the hydroxyl groups in flavonoids are important for optimum platelet inhibitory activities. In addition, the 4-C=O and B ring phenyl groups are less critical for the antiplatelet activity of these flavonoids. This structure-activity relationship of flavonoids with the modulation of platelet function may guide the design, optimisation and development of flavonoid scaffolds as antiplatelet agents.